Question 1

Suppose it were possible to lower a yellow sodium lamp toward the event horizon of a black hole.What would you see while watching from a safe distance?

Accepted Answer

A)  The brightness and color would each remain unchanged. 
B)  The light from the lamp would change to orange and then red. 
C)  The light would remain yellow, but there would be fewer and fewer photons being emitted from it. 
D)  The light from the lamp would change to green and then blue.

Question 2

A Type II supernova is the:

Accepted Answer

A)  collapse of a blue supergiant star to form a black hole. 
B)  explosion of a white dwarf in a binary star system after mass has been transferred onto it from its companion. 
C)  explosion of a red giant star as a result of a helium flash in the core. 
D)  explosion of a massive star after silicon fusion has produced a core of iron nuclei.

Question 3

When particle-antiparticle pairs are created just outside the event horizon of a black hole,one member can escape while the other enters the black hole.What is the name of this stream of particles leaving a black hole?

Accepted Answer

A)  Schwarzschild radiation 
B)  Kerr radiation 
C)  Planck radiation 
D)  Hawking radiation

Question 4

Where would you expect to find a core-collapse supernova?

Accepted Answer

A)  in a globular cluster 
B)  near a star-forming region 
C)  in a binary star system 
D)  near a black hole

Question 5

The X-ray bursts from an X-ray burster are caused by:

Accepted Answer

A)  hot spots caused by material falling onto the poles of a rotating neutron star. 
B)  explosive photodisintegration of iron nuclei on the surface of a neutron star. 
C)  explosive helium fusion on the surface of a neutron star. 
D)  explosive hydrogen fusion on the surface of a neutron star.

Question 6

Usually,ideal gases increase their pressure and volume when heated and decrease their pressure and volume when cooled.Do these rules apply to stars?

Accepted Answer

A)  No. Stars never follow the rules for ideal gases, even approximately. 
B)  Yes. Stars in all stages follow these rules quite closely. 
C)  No. Protostars have cores of degenerate matter in which the pressure is independent of the temperature. 
D)  No. White dwarfs are essentially degenerate matter in which the pressure is independent of the temperature.

Question 7

Which particles do NOT form a part of the flux of primary cosmic rays reaching Earth?

Accepted Answer

A)  electrons 
B)  neutrons 
C)  protons 
D)  positrons

Question 8

The structure of the deep interior of a low-mass star near the end of its life is a(n):

Accepted Answer

A)  carbon-oxygen core, a shell around the core where helium nuclei are undergoing fusion, and a surrounding shell of hydrogen. 
B)  inactive hydrogen core and a helium shell undergoing nuclear fusion surrounded by a carbon-oxygen shell. 
C)  turbulent mixture of hydrogen, helium, carbon, and oxygen in which only helium continues to undergo nuclear fusion. 
D)  helium core surrounded by a thin hydrogen shell undergoing nuclear fusion with very small concentrations of heavier nuclei.

Question 9

The diameter of a typical neutron star of 1 solar mass is predicted to be approximately:

Accepted Answer

A)  1 km. 
B)  that of an average city, a few kilometers. 
C)  that of the Sun. 
D)  that of Earth, 12,800 km.

Question 10

Measurements from distant galaxies indicate that supernovae should occur at a rate of five per century in a spiral galaxy such as the Milky Way,but only three have been recorded in this Galaxy in the past 1000 years.Explain.

Accepted Answer

A)  Most supernovae produce X-rays and radio waves, not visible light, and were hence invisible to earlier observers. 
B)  The majority of supernovae must have occurred in the plane of the Milky Way and hence were hidden from Earth by the dense gas and dust in the Milky Way plane. 
C)  The Milky Way Galaxy is somehow different, with much lower numbers of very massive stars in general, so many fewer stars have undergone supernova explosions. 
D)  Observers were not watching the sky carefully enough, particularly through the Dark Ages and over the past few centuries.

Question 11

At what location in the space around a black hole does the escape velocity become equal to the speed of light?

Accepted Answer

A)  the point where clocks are observed to slow down by a factor of 2 
B)  the central singularity 
C)  the event horizon 
D)  the point where escaping X-rays are produced

Question 12

A star of 25 solar masses spends roughly what percentage of its life as a main-sequence star? (See Table 12-1,Comins,Discovering the Essential Universe,6th ed.)

Accepted Answer

A)  about 7% 
B)  very little, less than 1% 
C)  93% 
D)  58%

Question 13

A star on the asymptotic giant branch (AGB)is a:

Accepted Answer

A)  cool main-sequence star. 
B)  blue supergiant. 
C)  star in its first red giant phase. 
D)  red supergiant.

Question 14

A Type Ia supernova is the:

Accepted Answer

A)  collapse of a blue supergiant star to form a black hole. 
B)  explosion of a red giant star as a result of a helium flash in its core. 
C)  explosion of a white dwarf in a binary star system after mass has been transferred onto it from its companion. 
D)  explosion of a massive star after silicon fusion has produced a core of iron nuclei.

Question 15

What is the event horizon of a black hole?

Accepted Answer

A)  the "surface" at which any object passing through it will leave with greater energy than it entered 
B)  the "surface" at which all events happen 
C)  the infinitesimally small volume at the center of the black hole that contains all of the black hole's mass 
D)  the "surface" from inside of which nothing can escape

Question 16

What property separates a black hole from the rest of the universe?

Accepted Answer

A)  a crystalline crust 
B)  the surface of the ergoregion 
C)  a singularity 
D)  an event horizon

Question 17

Where would you expect to see a supernova explosion?

Accepted Answer

A)  only in other galaxies with active nuclei 
B)  in the globular clusters surrounding the Milky Way Galaxy 
C)  in the plane of the Milky Way Galaxy 
D)  only in irregular galaxies, like the Large Magellanic Cloud, where star formation remains an ongoing process

Question 18

Nuclear fusion reactions of helium produce primarily:

Accepted Answer

A)  nitrogen and neon nuclei. 
B)  iron nuclei. 
C)  beryllium and lithium nuclei. 
D)  carbon and oxygen nuclei.

Question 19

A black hole can be thought of as:

Accepted Answer

A)  a star with a temperature of 0 K, emitting no light. 
B)  the point at the center of every star that provides the star's energy by gravitational collapse. 
C)  densely packed matter inside a small but finite volume. 
D)  a region with such a large mass density that even electromagnetic radiation cannot escape.

Question 20

What would the mass of a primordial black hole need to have been for it to be just disappearing now due to the loss of Hawking radiation?

Accepted Answer

A)  10 kg 
B)  10 million kg 
C)  10,000 kg 
D)  10 billion kg

Exam 12: The Deaths and Remnants of Stars